1,721,008 research outputs found
The Challenge of Conformational Isomerism in Cyclic Peptoids
No full textPeptoids (N-substituted glycine oligomers) are an increasingly important class of peptidomimetic foldamers with conspicuous bioactivities, high degree of resistance to enzymatic degradation, and ability to form stable secondary structures. The intrinsic rigidity of their oligoamide framework (due to n→π*, side chains NCα–H···O=C n→σ*, and backbone Cα–H···O=C interactions), can be magnified by cyclization to afford macrocyclic species with unexpected stereochemical, topological and biochemical attributes. In this minireview the implications of conformational chirality, a largely overlooked source of chirality in medium and large size cyclic peptoids, are addressed. The exploration of the unique structural and recognition properties of macrocyclic peptoid biomimetics unravels potential strategies for design and development of sequence-defined (cyclo)oligomers where conformational isomerism is an issue
Elaborate Supramolecular Architectures Formed by Co-Assembly of Metal Species and Peptoid Macrocycles
No full textPeptoids are a family of sequence-specific oligomers capable of mimicking the structure and function of polypeptides. The innate folding and self-assembly capabilities of peptoid oligomers can be enhanced by the presence of coordinated metal ions. In this work, we explore the co-assembly of water-soluble hexameric and tetrameric peptoid macrocycles with Na+ and K+ ions. Solid-state structures were solved for six cyclopeptoid-metal coassemblies by X-ray diffraction using single crystals grown from fully aqueous solutions. Subtle variations in the peptoid oligomer composition give rise to dramatic alterations in the supramolecular assemblies. Some structures feature extensively hydrated porous architectures that include unusual metal ion clusters. The ability to study the metallopeptoid structure at an atomic resolution in crystals obtained from an aqueous solution is an important advancement, as most previous peptoid crystal structures were obtained from nonaqueous or cosolvent solutions. These results will facilitate the design of peptoids and other foldamers for the assembly of supramolecular frameworks
Electrodeposition of Cu from acidic sulphate solutions containing cetyltrimethylammonium bromide (CTAB)
No full textRight- and left-handed PPI helices in cyclic dodecapeptoids
Full text linkEnantiomorphic right- and left-handed polyproline type I helices in four cyclic dodecapeptoids with methoxyethyl and propargyl side chains are observed for the first time by single crystal X-ray diffraction. The peculiar absence of NH⋯OC hydrogen bonds in peptoids unveils the role of intramolecular backbone-to-backbone CO⋯CO interactions and CH⋯OC hydrogen bonds in the stabilization of the macrocycle conformation. Moreover, intramolecular backbone-side chain C5 CH⋯OC hydrogen bonds emerge as a stabilizing factor
Cyclic hexapeptoids with N -alkyl side chains: Solid-state assembly and thermal behaviour
No full textThe solid state assembly of two cyclic hexapeptoids decorated respectively with five and six carbon N-alkyl side chains is analyzed by single crystal X-ray diffraction, intermolecular energies and lattice energy calculations. Thermal analysis and variable temperature X-ray powder diffraction were also carried out to analyze their thermal behaviour. The crystal structures of the two compounds feature architectural similarities, but also small relevant differences due to side chains-to-side chains interactions, which can explain the observed differences in the thermal properties. The compound with N-pentyl side chains exhibits a phase transition upon cooling down from room temperature to 100 K, while that with N-hexyl side chains features no phase transformation on cooling, instead a phase transformation occurs at 335 K upon heating
Design, synthesis, and hybridization of water-soluble, peptoid nucleic acid oligomers tagged with thymine.
No full textThe preparation of a new class of backbone-modified PNA mimetic incorporating thymine is described. Target dipeptoid monomer 21 was synthesised from an N-[2-(thymin-1-yl)ethyl]glycinate ester and a properly protected iminodiacetic acid. The distinctive structural motif in the backbone is acarboxy group, inserted to impart water solubility to the oligomer. Two achiral oligopeptoid sequences (8-mer and 12-mer), characterised by the shift of the amide carbonyl group away from the nucleobase, were efficiently assembled according to solid-phase synthesis protocols. Thermal denaturation studies showed that the two homopyrimidine oligopeptoids do not effectively hybridise with complementary sequences of DNA and RNA or fully synthetic (2,4-diamino)triazin-6-yl-tagged peptoid 22. A possible reason could reside in the concurrent unfavourable influence of the anionic N-(carboxymethyl) moieties and the flexible nucleobase/backbone ethylene linker
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